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Friday, 22 April 2016

Climate Change is Bleaching the Great Barrier Reef Out of Existence

“Extinction.
….It’s a hard, tough thing to consider. One of those
possibilities people justifiably do not want to talk about.... Our
aversion to the topic likely stems from our own fear of death. Or
worse — the notion that the entire human race might eventually be
faced with such an end. ....But extinction is a threat that we’ll
see arising more and more as we force the world to rapidly warm.”

I
have criticised Robert Fanny recently – and I think justifiably so
– but kudos for mentioning the E word and publicly contemplating
the possibility

We
all deal with this horror in our own way.

A
Death of Beauty — Climate Change is Bleaching the Great Barrier
Reef Out of Existence

It’s
a hard, tough thing to consider. One of those possibilities people
justifiably do not want to talk about. This notion that a creature
we’re fond of and familiar with — a glorious living being along
with all its near and distant relatives — could be entirely removed
from the web of existence here on Earth.

Our
aversion to the topic likely stems from our own fear of death. Or
worse — the notion that the entire human race might eventually be
faced with such an end. But extinction is a threat that we’ll see
arising more and more as we force the world to rapidly warm. For
species of the world now face existential crisis with increasing
frequency as atmospheric and ocean temperatures have risen so fast
that a growing number of them have simply become unable to cope with
the heat.

The
damage comes in the form of extreme ocean heat. Heat resulting from
global temperatures that are now well in excess of 1 degree C above
preindustrial times. Heat that has forced ocean temperature
variability into a range that is now lethal for certain forms of sea
life. Particularly for the world’s corals which are now suffering
and dying through the worst global bleaching event ever experienced.

The
Worst Global Coral Bleaching Event Ever Experienced

During
2014 the oceans began to heat up into never-before seen temperature
ranges. This warming initiated a global coral bleaching event that
worsened throughout 2015. By early 2016 global surface temperatures
rocketed to about 1.5 C above 1880s averages for the months of
February and March. These new record high temperatures came on the
back of annual carbon emissions now in the range of 13 billion tons
each year and at the hotter end of the global natural variability
cycle called El Nino. Both the atmosphere near the land surface and
the upper levels of the ocean experienced this extreme warming.

In
the ocean, corals rely on symbiotic microbes to aid in the production
of energy for their cellular bodies. These microbes are what give the
corals their wild arrays of varied and brilliant colors. But if water
temperatures rise high enough, the symbiotic microbes that the corals
rely on begin to produce substances that are toxic to the corals. At
this point, the corals expel the microbes and lose their brilliant
coloration — reverting to a stark white.

(A
vast region of the world’s ocean system continues to experience
coral bleaching. In area, extent, height of extreme temperature, and
duration, the current global coral bleaching event is the worst ever
experienced by a good margin. As global temperatures continue to warm
due to ongoing fossil fuel burning and related carbon emissions,
widespread coral bleaching is likely to become an annual occurrence.
Temperatures have risen far enough and will continue to rise for long
enough to set about ocean conditions that will result in mass coral
die-offs around the world. Image source: NOAA.)

Bleaching
isn’t necessarily lethal to corals. However, once the microbes are
gone, the corals have lost a key energy source and will eventually
die without them. If ocean temperatures return to normal soon enough,
the corals can begin to accept the symbiotic microbes back, return to
a healthy cellular energy production, and survive — albeit in a
weakened and more vulnerable state for some time to come. But if
ocean temperatures remain too warm for an extended period, then the
corals will be deprived of energy and nutrients for too long and they
will inevitably perish.

The
kind of coral bleaching event that we’re experiencing now is a mass
killer of corals. Not simply due to the heat itself, but due to the
long duration of the extreme temperature spike. By late February,
many ocean scientists were very concerned about the already severe
damage reports that were starting to come in. At
that time, NOAA issued this warning:

“We
are currently experiencing the longest global coral
bleaching event ever observed.
We may be looking at a 2- to 2½-year-long event. Some areas have
already seen bleaching two years in a row.”

93
Percent of Great Barrier Reef Affected by Bleaching

By
late February, the level of concern for the Great Barrier Reef was
palpable. Stark reports were starting to come in from places like
Fiji — which had experienced two years of severe bleaching — and
Christmas Atoll about 1,300 miles south of Hawaii — whose
reported losses were best described as staggering.
So far, the worst of the hot water had stayed away from Australia’s
great reef.

But
by early March a plume of very extreme ocean heat began to appear
over The Great Barrier Reef’s northern sections. Sea surface
temperatures spiked to well above, a dangerous to corals, 30 degrees
Celsius for days and weeks. This 30 C or greater heat extended deep —
hitting as far as 50 meters below the ocean surface over the reef.
And it rippled southward — hitting section after section until few
parts of the reef were spared.

“Tragically,
this is the most remote part of the Reef, and
its remoteness has protected it from most human pressures: but not
climate change.
North of Port Douglas, we’re already measuring an average of close
to 50% mortality of bleached corals. At
some reefs, the final death toll is likely to exceed 90%.
When bleaching is this severe it affects almost all coral species,
including old, slow-growing corals that once lost will take decades
or longer to return (Emphasis added).”

But
with the oceans still warming, and with more and still worse coral
bleaching events almost certainly on the way, the question has to be
asked — will these corals ever be afforded the opportunity to
recover?

When
ocean surface temperatures warm into a range of 2 C above 1880s
levels — the kind of severe global heating that could arise under
worst-case fossil fuel emissions and related warming scenarios by the
mid 2030s — corals in the Great Barrier Reef are expected to
experience bleaching on an annual basis. Every year, in other words,
would be a mass coral bleaching and die-off year.

(Sea
surface temperatures and temperatures withing the top 50 meters of
water over the Great Barrier Reef of Australia rose to 3-4 C above
average during the austral Summer and Fall of 2016. These record
temperatures lasted for weeks in some regions setting off the worst
coral bleaching event the Great Barrier Reef has ever seen. By
mid-Century, coral bleaching and mass die-offs are likely to occur on
an annual basis as global temperatures surpass the 1.5 C and 2 C
thresholds. Image source: Earth
Nullschool.)

Globally,
bleaching events under even moderate fossil fuel emissions scenarios
would tend to take up much of the Equatorial region on an annual
basis by mid-Century. Events that can, during single years, wipe out
between 90 and 95 percent of corals at any given location. A handful
of corals will likely survive these events — representing a remote
and far-flung remnant who were simply a bit hardier, or lucky, or who
had developed an ability to accept microbes that are tolerant to
warmer temperatures. But these hardy or fortunate few would take
hundreds to thousands of years to re-establish previous coral reef
vitality even if other harmful ocean conditions did not arrive to
provide still more damage.

As
coral bleaching expands at the Equator due to increasing rates of
ocean warming, increasing levels of carbon dioxide in the atmosphere
causes oceans to become more acidic. Cooler waters at the poles are
better able to transfer gasses into the ocean’s waters. And higher
levels of carbon dioxide in the world ocean results in a growing
acidity that is harmful to corals. Increasing levels of ocean acidity
thus creep down from the poles at the same time that bleaching events
move up from the Equator.

If
fossil fuel emissions continue, by mid-Century atmospheric carbon
dioxide levels in the range of 450 to 500 parts per million will have
provided a never-before seen spike to ocean acidity. Such high ocean
acidity would then provide a second severe blow to corals already
devastated by bleaching events. It’s a 1-2 punch that represents a
mass extinction threat for corals this Century. And we’re starting
to see the severe impacts ramp up now.

(Coral
bleaching is a severe threat to tropical coral reefs now. But CO2
potentially hitting above 500 parts per million, according to a 2014
study, risks a complete loss of equatorial coral reefs by 2050 to
2100. Between bleaching and acidification, there’s no way out for
corals so long as fossil fuel burning continues. Image source: Threat
to Coral Reefs From Ocean Acidification.)

The
only hope for stopping this ever-expanding harm is a rapid cessation
of fossil fuel emissions. And we owe it to the corals of the world,
the millions of species that depend on them, and the hundreds of
millions of people whose food sources and economic well being come
from the corals.

“And
Then We Wept”

When
researchers told students of the extent of harm to corals upon the
Great Barrier Reef,the
students were reported to have wept.
And with good reason. For our Earth had just experienced a profound
death of beauty. A death of a vital and wondrous living treasure of
our world. A priceless liquid gem of our Earth. A wonder that gives
life to millions of species and one that grants both food and
vitality to Australia herself. For if the reef goes, so does a huge
portion of the living wealth of that Nation and our world.

Sadly,
the tears will just keep coming and coming as these kinds of events
are bound to worsen without the most dramatic and urgent global
actions. The current and most recent catastrophe is thus yet one more
in a litany of wake up calls to the world. But will we hear it loud
and clear enough to act in ways that are necessary to ensure the
corals survival? And what of the billions of creatures and of the
millions of humans too that depend on the corals? Do we care about
them enough to act?

(Please
support public, non-special interest based science like the essential
work that has been provided by Terry Hughes over so many years and
decades. Scientists like Terry provide a vital public service. For
years, they have given us a clear warning of a very real and ever
more present danger. A warning that gives us a fleeting opportunity
to respond to events before we lose the richest living treasures of
our world. Before we are bereft of our ability to continue to make
livelihoods as environmental abundance and the related regional and
global life support systems are irreparably damaged.)